Data & Methodology — Seminole County

Full contaminant data, sample history, and sourcing for Seminole County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

1194 well testing events on record, covering 21 analytes. Data spans 1944 to 2025.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. FL Avg
Iron 392 1973–2025 100%
10% of limit ↓ 95% below
Chloride 469 1973–2025 100%
10% of limit ↓ 79% below
PFOS municipal 50 2023–2025 14%
140% of limit ↓ 34% below
PFOA municipal 50 2023–2025 12%
120% of limit ~ typical
Sulfate 450 1973–2025 100%
7% of limit ↓ 74% below
Arsenic 368 2013–2025 100%
5% of limit ↓ 62% below
Lead 368 2013–2025 100%
0% of limit ↓ 89% below
Manganese 368 2013–2025 100%
9% of limit ↓ 67% below
Nitrate 599 1973–2022 100%
1% of limit ↓ 84% below
PFHxS municipal 50 2023–2025 18%
33% of limit ↓ 36% below
PFNA municipal 50 2023–2025 0%
— —
Nitrite 600 1973–2022 100%
2% of limit ↑ 22% above
HFPO-DA (GenX) municipal 50 2023–2025 0%
— —
Fluoride 118 1973–2025 99%
2% of limit ↓ 72% below
pH 562 1973–2025 100%
— ~ typical
Sodium 450 1973–2025 100%
— ↓ 79% below
PFBS municipal 50 2023–2025 10%
— ↓ 21% below
Fecal Coliform 46 2013–2021 100%
— ~ typical
E. coli 38 2021–2025 100%
— ~ typical
Total Coliform 85 2013–2025 100%
— ~ typical
Hardness 14 1973–2000 100%
— ↑ 110% above

Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across FL.

Compare your result with Seminole County

Of the 368 arsenic tests on record for Seminole County (2013–2025), 0% found none, and half were below 0.5 µg/L.

Of the 469 chloride tests on record for Seminole County (1973–2025), 0% found none, and half were below 25.5 mg/L.

Of the 118 fluoride tests on record for Seminole County (1973–2025), 1% found none, and half were below 76.5 µg/L.

Of the 392 iron tests on record for Seminole County (1973–2025), 0% found none, and half were below 30 µg/L.

Of the 368 lead tests on record for Seminole County (2013–2025), 0% found none, and half were below 50 ng/L.

Of the 368 manganese tests on record for Seminole County (2013–2025), 0% found none, and half were below 4.42 µg/L.

Of the 599 nitrate tests on record for Seminole County (1973–2022), 0% found none, and half were below 51 µg/L.

Of the 450 sulfate tests on record for Seminole County (1973–2025), 0% found none, and half were below 16.8 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 392 samples
  • Chloride 469 samples
  • Sulfate 450 samples
  • Arsenic 368 samples
  • Lead 368 samples
  • Manganese 368 samples
  • Nitrate 599 samples
  • Nitrite 600 samples
  • Fluoride 118 samples
  • pH 562 samples
  • Sodium 450 samples
  • Fecal Coliform 46 samples
  • E. coli 38 samples
  • Total Coliform 85 samples

Limited data (<15 samples) — interpret with caution

  • Hardness 14 samples

No private-well PFAS data for Seminole County

We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Seminole County. PFAS has been detected in local public water systems (UCMR 5 data) — indicated by the "municipal" badge in the table above — but this does not directly indicate private well contamination. PFAS testing for private wells requires a dedicated lab panel (~$300–$500). If you are near a military base, airport, or industrial site, consider testing proactively. Learn more about PFAS →

Public vs. Private Water in Seminole County

60 Active public water systems
510,279 Residents on public water
6% Households on private wells

Public water systems in Seminole County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.

CDC Health Outcome Correlations

Where contaminants detected in Seminole County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.

Contaminant Associated Condition Seminole County Prevalence FL Average Source Year
Arsenic Cancer prevalence 6.5% 6.8% 2020
Arsenic Kidney disease rate 2.6% 3.4% 2020
Lead Heart disease rate 5.3% 7.7% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Seminole County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

Methodology

Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.

Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.

State comparison uses the median of county median values across all counties in FL with at least one sample for that analyte.

Last updated: 2026-08-12

Full methodology →